


Bot/Bonefriends

by Kinky_Parentheses



Category: Undertale (Video Game)
Genre: Anal, Creampie, Cum Inflation, Dildos, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Vagina (Undertale), First Time, Fluff, Fontcest, M/M, Multi, Polyamorous relationship, Public Humiliation, Robot Kink, Smut, Soul Sex, Spitroasting, Tribbing, actually quite a bit of fluff, cumflation, healthy relationship, mettasans, papyton
Language: English
Status: Completed
Published: 2019-10-23
Updated: 2019-10-23
Packaged: 2020-12-28 23:44:14
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 6
Words: 12,324
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21145208
Author URL: https://archiveofourown.org/users/Kinky_Parentheses/pseuds/Kinky_Parentheses
Summary: Bad title, blah blah. Just a semi-loose chronological timeline of when Sans started dating Papyton and how things proceeded afterwards.





	1. Chapter 1

**Author's Note:**

> Undertailsoulsex/soulscum posted a prompt for MettaFontcest literal years ago, and I finally got around to finishing it. You have them to thank for this monstrosity X3

Sans always loved how happy Mettaton made his brother, and when Papyrus’ happiness peaked upon beginning a relationship with the robot, he was overjoyed. He saw it as his job to keep Papyrus as happy as he could, but he couldn’t do it alone. While he wasn’t as big of a fan of Mettaton as Papyrus was, he gradually warmed up to him during his visits to their chilly house, simply grateful for the much-needed help in giving Papyrus all the love possible. Papyrus and Mettaton dated for about a year before Papyrus started wanting things to change. He was growing older and he was realizing the self-sacrifice his brother went through to ensure his happiness, to the point where Sans didn’t own a bedframe as he had only cared to get Papyrus a racecar bedframe. Mettaton was concerned when Papyrus entered this phase of realisation that Sans had given up all the comforts he could to make his brother’s life as cushy as possible, but one day, while Sans was visiting Grillby’s and the couple was lounging on the couch watching reruns, Papyrus decided to make known an idea he had been formulating.

“HEY METTATON.”

The robot took his screen from the image of himself on the television, pushing himself up against the arm of the couch so his blocky form could properly face Papyrus. He remained in his rectangular form during his visits both because Papyrus had always loved his rectangular form the most, and because in this household, there were certain benefits to lacking a mouth.

“Yes, darling?” His screen winked blue and green passively, wondering what it was that had Papyrus looking so sheepish. “Is something wrong?”

Papyrus scratched the side of his skull, not entirely sure how to go about phrasing his feelings. “KIND OF? I’M REALISING LATELY HOW MUCH SANS HAS DONE FOR ME ALL MY LIFE, AND HOW MUCH I TAKE HIM FOR GRANTED. HE’S ALWAYS PUTTING ME BEFORE HIM, AND IT UPSETS ME THAT I NEVER LEARNED HOW TO TAKE CARE OF HIM THE WAY HE TAKES CARE OF ME.”

Mettaton reflected for a moment. Papyrus had grown so much in just the year they had been dating, and he was proud of him for that. “So what do you want to do for him? What do you think he’d like for you to do?”

Papyrus reached out his hand for Mettaton to take, and he did. “YOU MAKE ME INCREDIBLY HAPPY, AND I MAKE SANS INCREDIBLY HAPPY, SO I WONDERED IF YOU’D BE OKAY WITH LETTING HIM DATE US. I THINK MAYBE HE WOULD BE HAPPIER IF I PAID MORE ATTENTION TO HIM AND LISTENED TO HIM MORE, AND I THINK THAT HE WOULD TELL ME MORE THINGS FOR ME TO LISTEN TO. WHAT DO YOU THINK?”

Mettaton’s screen blinked from red to yellow, reflecting his inner thoughts as they flew around. That wasn’t what he had been expecting! Papyrus was known for being a bit naïve, but… “Are… Are you sure he’d be okay with dating his brother? Are YOU okay with dating your brother?”

Papyrus cocked his head. “IT DIDN’T REALLY OCCUR TO ME, BUT SURE. I’D BE FINE WITH DATING HIM IF HE WOULD BE HAPPIER BECAUSE OF IT. WE’VE BEEN LIVING TOGETHER ALL OUR LIVES ANYWAY, AND WE FUNCTION THE WAY A MARRIED COUPLE WOULD, BUT WITHOUT THE ROMANCE. JUST THE CLEANING AND THE BILLS.”

Mettaton considered it. He supposed it made sense, and the thought of dating both the skeleton brothers did sound appealing. His screen shifted colors warmly in what could have been a smile and he squeezed Papyrus’ hand. “I don’t mind dating him if you don’t mind dating him. Let’s try it.”

Papyrus’ grin could have powered cities. “THANK YOU METTATON! SHOULD WE INVITE HIM TO JOIN US WHEN HE GETS HOME, OR DO YOU THINK WE SHOULD WAIT?” He was practically bouncing in his seat, pleased at the development.

Mettaton’s screen gently pulsed yellow and green. “We can ask him when he gets home if you want, Sugarskull.” The more he thought about it, the more the idea of dating the stocky skeleton excited him. Sans was a part time employee at his resort so they had been in the same environment since before Papyrus and he started dating. In fact, Sans was the reason he met Papyrus at all, when Papyrus had attended one of Sans’ skits and Sans allowed him backstage, and Mettaton had just happened to be there. His screen shifted to a rosy pink as he remembered how excited Papyrus had been to meet him, how utterly unique he was in that he loved Mettaton for the sheer sake of his person, though this had not always been the case. Papyrus wanted to see Mettaton more often outside his performances, and Mettaton had been enthralled by Papyrus’ unpredictability. Usually fans would tire of him once he dropped his stage façade, but not only did Papyrus seem willing and open to seeing more of the private Mettaton, he made himself incredibly interesting compared to the rest of his fans. Most fans would bring him flowers or food, but Papyrus was so perceptive that he remembered things Mettaton had said in passing on some show or another years ago about his affinity for puzzles. They bonded over puzzles quite often, and Papyrus would often bring one brain-teaser or another to their dates. Mettaton felt himself falling for him as he watched those sockets twinkle in delight while they solved their puzzles. Papyrus had never requested him to change into his EX form as opposed to his BETA form since he preferred the BETA form so much, but Mettaton’s fans had all asked at one point or another for Mettaton to show his body to them. It was refreshing to be with someone who didn’t mind one way or the other.

Mettaton was snapped out of his thoughts when the front door opened, his screen flashing yellow with a red exclamation mark as the famous Metal Gear sound effect played through his speakers. Damn Alphys for programming him with her browsing history in mind. Papyrus was practically vibrating next to him as Sans lumbered into the kitchen. The sound of the fridge opening and closing was heard by both of them, and Sans walked out of the kitchen stretching a moment later. He seemed about to greet the couple but stopped at the look on Papyrus’ face. Mettaton snorted at the scene, Papyrus’ eyesockets were literally sparkling as if they held tiny galaxies.

“hey bro, mettaton.” Sans could barely say those words before Papyrus started gesturing for him to come over.

“SANS! METTATON AND I HAVE SOMETHING TO ASK YOU!” Sans stood in front of Papyrus, eyesockets level despite the fact that Papyrus was sitting down. Papyrus took Sans’ hands and stood up. “WE WANT TO KNOW IF YOU WOULD LIKE TO DATE US!”

Sans’ eyesockets widened. His gaze darted to Mettaton and back to Papyrus’s gleaming face, obviously trying to figure out if it was a trick. He found no malintent in his brother’s eyes, but shook his hands away and sat down between his brother and his botfriend. He covered his mouth and nasal bone with both hands and stared at his feet for a second.

“Sans? Are you okay?” Mettaton reached out to Sans’ hand and squeezed it comfortingly. This was not the reaction he had been expecting.

“BROTHER, YOU DON’T HAVE TO DATE US IF YOU DON’T WANT TO. WE CARE ABOUT YOU AND THOUGHT YOU’D WANT TO BE INCLUDED, BUT IT’S FINE IF YOU DON’T! THE GREAT PAPYRUS WILL LOVE YOU NO LESS IF YOU DECLINE.”

Sans raised his head and looked into Papyrus’ worried face, his eyesockets moist. “no no, i want to, i just--” he dipped his head as he felt a sob about to wrack through his voice, raising it again just as quickly with a watery grin, “i never thought you’d ask. i didn’t think you’d want… me. i would love to date you both. i always have.”

Papyrus brightened, his cheer returning so quickly he had to displace it to Sans in the form of a hug. Mettaton’s screen was yellow with a big, red heart as he watched the scene, which he joined as Papyrus waved him over. He had retracted his wheel while relaxing, so he hopped over to the brothers and wrapped his arms around both, his screen blinking rhythmically.

“i’m so glad,” Sans mumbled. He reached up and kissed Papyrus on the cheekbone, then Mettaton’s screen.

After the three separated, the rest of the night was relatively quiet as they cuddled up on the couch and talked over a movie or two. Mettaton’s hard edges did nothing to discomfort the two skeletons, who themselves had hard edges and were used to it. Every time one of them shifted, bones clacked together and metal clanked, and it was like their own little percussion. Eventually Mettaton had to leave, and soon after that the brothers were thinking of retiring to their rooms. Papyrus got up and stretched, his bones popping still as he turned off the television. Sans stretched too, but only enough so that his arms were extended toward Papyrus. “carry me.”

Papyrus smiled and sighed. He usually did carry Sans to his room, but usually Sans had already fallen asleep on the couch. He bent down and gracefully picked Sans up, holding him koala-style. He stepped carefully up the stairs and turned off the lights at the top, but instead of carrying Sans to his room like usual, he brought Sans into his own room and gently set him on his racecar bed. Papyrus still slept in his battle body and Sans didn’t change his clothes to sleep either, so little needed to be done before they both settled in for the night. Papyrus took the side of the bed closest to the wall, flicking the lightswitch on the wall at the foot of the bed. He could see Sans’ eyelights still blinking up at the ceiling, and Sans seemed uncomfortable.

“ARE YOU OKAY WITH SLEEPING IN HERE WITH ME?” Papyrus realised he hadn’t even asked.

Those white eyelights shifted toward him. “of course, i was just uh, y’know. thinkin’ about us. i don’t know how far you and mettaton have gone, so i just wanted to make sure it wouldn’t be weird if i wanted to do stuff.”

“TONIGHT? WHAT KIND OF STUFF?”

“not bad stuff, i just wanted to cuddle is all.”

Papyrus smiled easily. “OF COURSE, BROTHER. I WOULD GREATLY ENJOY THAT.”

“heh, thanks bro.” Sans rolled on his side, facing away from Papyrus, and pushed his back into his brother’s chest while he curled into fetal position. Papyrus held his brother across his ribcage, trailing over the shirt-covered bone gently as he started to fall asleep.

“mmm, i love you, paps.” Sans tilted his head up to look at Papyrus, whose teeth clanked on his forehead affectionately.

“I LOVE YOU TOO, BROTHER.” And so their first day of dating ended peacefully.


	2. Chapter 2

Sans seemed much happier after he started dating Papyrus and Mettaton. Mettaton couldn’t come over every day but the skeletons saw him every day on their television, and they were together often enough that Mettaton’s celebrity schedule didn’t get in the way too much. Papyrus and Sans became more affectionate around their house, and Sans’ shoulders eased when he realised he could finally act on his love for Papyrus as he had wanted to for so long. He often clung to him while he cooked, nuzzling his nasal bone into Papyrus’ spine. Sans was more honest with Papyrus and talked about his days more, and Papyrus listened, and the more he heard the more he understood about his brother. The two were together more often than all three of them at once, but that was true before Sans started dating them. He was just as affectionate to Mettaton when he came over as he was to Papyrus, and he found that he loved it when Mettaton came over even more because watching Papyrus in the presence of his two favorite people in the world was just a beautiful sight.

The first time the three of them brought things to the bedroom was a little strange for all of them. It was about a month after Sans joined, and it was Papyrus and Mettaton’s first time together. All of them were new and nervous. Sans and Papyrus decided it would be best if they focused on Mettaton, both out of a curiosity for the robot’s anatomy in his EX form since skeleton anatomy was familiar already, and because they simply weren’t sure if they were ready to touch each other that way yet. They started by leaning Mettaton against Sans’ sturdy, kneeling form with Papyrus hovering on top of him. Between the two, Mettaton’s soul was absolutely dripping. Sans’ baritone whispers on his neck, biting with hidden fangs on the synthetic flesh, and Papyrus’ deft fingers crawling and grabbing onto his body were both driving him delirious and overwhelmed. He was used to having all eyes on him, had even had multiple partners in his bed before, but this was something else. His speakers were crackling and his LED pupils flashed and dimmed.

Both skeletons were clothed, but he couldn’t stand the heat any longer when they kissed over his shoulder. He activated his pussy manually and two slates between his legs split apart, compartmentalising into his legs while his vulva clicked into place, already glistening. Papyrus noticed immediately and took only a moment to remove his gloves while making excited eye contact with Mettaton before cupping his slender fingers against the pink-tinted folds. He rubbed lengthwise and spread him apart, then gave his clit a quick few rubs to the surprised cry of Mettaton. He felt his cunt gush a bit more as he watched Papyrus bring his soul-slickened fingers to his mouth and curl his long, orange tongue around them. Papyrus’ sockets widened at the taste, a huge, doofy grin appearing.

“SANS! OUR BOYFRIEND’S SOUL IS BUBBLEGUM FLAVORED!” Papyrus roughly shoved his fingers in Mettaton’s cunt without warning, making him choke and his eyes flash hearts as he was quickly filled and emptied, but Papyrus didn’t leave him empty and shoved his other fingers in him while he presented his pink-slicked fingers to Sans. Sans made a surprised noise at the smell of them, and Mettaton heard him licking and suckling on his brother’s fingers to taste him.

“he sure does, bro. sounds like you’re fingering him pretty good. bet you could give him something more if ya really wanted to get a good taste.”

Papyrus’ eyelights sparkled and he briefly looked Mettaton in the eye before quickly stooping down to his pussy and shoving his tongue as far up him as he could after whipping out his fingers. Mettaton arched up and cried out at being so roughly handled by his perky boyfriend and found himself suspended in air. Sans’ wrist was resting on the chassis of his soul and his hand was hovering above it, keeping him suspended above the bed with his blue magic. This put his pussy at mouth-level with Papyrus and he took great joy in grabbing his hips and pulling him as close to his face as he could, throwing legs over shoulders and groping his ass as he pleased. His nasal bone rubbed at Mettaton’s clit as he practically devoured him, hearts in his sockets. If Mettaton wasn’t a slut for pain he’d have advised Papyrus against pressing his sharper facial features that hard on his genitals but his mouth was occupied sputtering and moaning out what his boyfriends could only assume were obscenities, but his voice was glitching and his own ability to speak was so far gone it was all but impossible to tell what was going on in his pretty head.

All he was aware of was Papyrus’ fucking tongue destroying any coherent thought, Sans’ quiet chuckles while he kissed anywhere he could (without moving), and how embarrassingly close he already was. Sans’ other hand held him gently on the clavicle.

“C-CUUUHMMING!!! PAPYYYRUS!!! FUCK!” Mettaton felt his whole body tighten up and he grasped at Sans’ hand on his neck as he squirted blue-tinted cum on Papyrus’ face and in his mouth.

“Ah...”

Papyrus leaned back and dragged his tongue across his face to clean it of his new lover while Sans spun him in the air so his legs were under him again, then abruptly dropped him on the mattress and shoved his head down to Papyrus’ shorts. Sans straightened up and pulled his hard dick out of his shorts, already lining up while Mettaton got the hint and scrambled to yank down Papyrus’ shorts and get his lips on the glowing orange cock that greeted him via smack on the face.

“NYEH!” Papyrus’ cock was down his throat before Sans could ask if he was ready to go again. With Sans kneeling behind Mettaton, hands on his hips as he thrust into the robot, and Mettaton’s head in between Papyrus’ thighs, Mettaton let his eyes roll up in his head and grasped for Papyrus’ hands to pull his hair. The choking sensation from swallowing Papyrus’ dick was something that definitely wasn’t required in his design but was something he’d begged a flustered Doctor Alphys to let him keep. He swallowed and clenched his pussy as much as he could to make his boyfriends cum, Sans setting a slow, hard pace and Papyrus generally just being energetic in shoving his head down repeatedly. His screams through his chest speaker were joined by the quiet grunts from Sans and the adorable moans from Papyrus. Quite suddenly, Papyrus finished in Mettaton’s mouth and watched intently as Sans pulled Mettaton close so he was riding him, then kissed him so Papyrus’ cum was shared between them. Mettaton finished with a glitched cry and Sans followed after, flooding his pussy to his soul chamber with bright blue splooge.

~~~

After the brothers extricated themselves from their robot and all got cleaned up, they all went to bed at Sans’ request. Mettaton was cuddled between Sans and Papyrus, and the former two slept while Papyrus simply admired his sleeping boyfriends. He had had his daily four hours of sleep already and was content just watching them sleep, but he made sure to plug Mettaton in just in case they woke up ready for more. They were satisfied, but things would only get better from there. As Mettaton’s arms noodled around him, he found himself excited to see all they could do together, what fantasies they’d allow him to act out with him-

…

Well, he hoped he wasn’t getting too eager too quickly.


	3. Chapter 3

Mettaton visited quite often before dating Sans, but it was then that he realised he should probably start making his visits more like coming home than just visiting his bonefriends’ house. He brought a pillow and a pink, fluffy blanket, along with some cute pajamas and the boa Alphys had given him, since he didn’t really own any other clothes besides what he advertised, but it would be too tacky to wear his own brand outside advertisements. Mettaton loved the boa and didn’t feel the need to wear clothes other than it on occasion, like on date nights and such. He thought he couldn’t be happier when it was just him and Papyrus, but the dynamic of the relationship changed with Sans. In Sans’ and Papyrus’ relationship as brothers, he could see the changes that were occurring. Sans seemed brighter, his smiles more genuine, twinkles in his sockets Mettaton thought only Papyrus was capable of. Him and Sans were comfortable with each other, since Mettaton was Sans’ boss, but until he started dating him it had never been much more than smalltalk and checking up on his next skit. He had to admit, he hadn’t been in love with the small skeleton beforehand, but as time went on he enjoyed his presence more and more. Sans seemed enthralled by his inner workings, and would fall asleep on his chest or screen listening to the whirrs and clicks of fans and gears somewhat consistently. Sans seemed to know quite a bit about machinery, which was odd, considering Papyrus was the only one who had shown interest in what made Mettaton tick before. Papyrus was a born engineer, but now Mettaton wondered if Sans had picked it up from him or the other way around.

Regardless, sometimes Mettaton felt like they wanted to pick him apart as their own little research project, even if they never said anything about it. The thought sent shivers up his mechanical spine. He didn’t know what was in him or how his body worked, but if he opened up to them, they would be able to play with them in ways he had never felt before…

Well. Let’s just say Mettaton enjoyed the thought of dating two skilled engineers.

Sans shifted against his warm chestplate, his arm curling around Mettaton’s thigh briefly as he regained consciousness. Papyrus was out training with Undyne and doing errands, so they were alone for a while. Sans had taken the opportunity for guilt-free sleep, and Mettaton was comfortably watching him. He was quite cute when he was asleep, with such a relaxed face. Mettaton thought the grin was permanent, but it closed a bit so only his front teeth were showing. Mettaton wasn’t entirely sure he wanted to know how the bone around his teeth worked in covering his teeth like a pair of lips would, so he saved it for another day. Was Sans saying something?

“you there?” Sans cocked his head as Mettaton refocused, his pupils whirring slightly as they resized themselves.

“Hm? What was that, darling?” He thought it was funny that he was limited in how much attention he could pay to more than one task at a time, but he supposed that was more of a listening fault than a design error. Not all his functions were robotic, after all.

“i said i was thinking that we could mess around in my room before paps gets home.” He shrugged. “didn’t know if you were up for it.”

Mettaton grinned devilishly, scooping Sans up by the backs of his thighs and kissing him while he made for the stairs. His teeth weren’t much good for anything in this regard, but the thick, blue tongue was talented enough that Mettaton caught himself about to ask why at some points. He broke the kiss as he began climbing the stairs, putting his chin on Sans’ shoulder so he wouldn’t try distracting him before he got to the top.

“I assume that by ‘mess around’, you meant I’d get to touch you instead of just carry you up to your room so you could sleep.” It had happened before.

Sans bit and licked Mettaton’s fleshy neck, making him stutter in his steps just as he reached the top of the stairs. “coincidentally, that is exactly what i mean.”

Mettaton shuddered and picked up his pace, pushing Sans’ door open with a wide swing of his hips. He wasn’t two steps into the room before he threw Sans on his bed, kneeling over him with his lips just far enough away as to tempt Sans to push himself up onto his elbows and kiss him himself. Mettaton curled his hand around Sans’ skull, ghosting his fingers over the back of it while their tongues and teeth and lips fought in a painful, lovely dance. It wasn’t far off to say that Sans understood and enjoyed helping Mettaton with his less vanilla interests, and while bedding Papyrus was fun, he didn’t seem to have much interest in anything too deviant. Inflicting pain upon one’s partner was too deviant for Papyrus, but perhaps one day Mettaton and Sans could share this with him, when Papyrus seemed ready to learn the ways of sadism and masochism.

Mettaton’s hand grasped Sans’ right iliac crest, his nails pressing into it through his gloves. Sans groaned at the dull, tight pain, grasping at Mettaton’s back and arching himself off the bed to try to bring them closer together. Mettaton’s lips disconnected with Sans’ mouth, his tongue still sticking out as he licked a long, wet stripe up the entirety of Sans’ cervical vertebrae. He mewled pathetically and tossed his head to the other side to give Mettaton and his smooth mouth more room. Sans was so tiny and Mettaton so large that to lean over him, Mettaton’s hips were in the air and Sans’ feet only went down to Mettaton’s waist while his mouth was on his neck. Mettaton had moved further down and was biting at Sans’ shoulder and collarbones, leaving tiny indentations for him to suck. The hand on Sans’ iliac crest moved to remove Sans’ shorts, and intentionally or not, Sans’ hips leapt off the bed as a reaction to Mettaton giving his pelvis a squeeze.

Mettaton could swear he could already feel his soul dripping. Sans was usually so cool and in control, so to see him submit entirely was a surprise to say the least. Or, it would have been if Sans also hadn’t been one to lay back and take it even in regular situations. That wasn’t to say Sans couldn’t be absolutely vile when he was on top, but he seemed to enjoy being led as opposed to leading. Mettaton was fine with this, as long as he got to toy with Sans and make him writhe for him the way he was. Mettaton chuckled to himself, kissing Sans just under his lifted jaw. “Mmm, you really love this, don’t you darling?”

Sans’ hand came to rest on the back of his head as Mettaton moved to kiss his sternum over his shirt while he played with his pelvis and took off his shorts. His sternum was so sensitive, he knew why but the thought was completely blocked in his haze of pleasure as he cried out, “yes! Yes!”

Mettaton tossed the shorts to the floor along with his own gloves-- usually he would make a show of taking them off with his mouth, but not today-- and caressed Sans’ iliac crests with both hands, lifting it up and tilting it slightly as he unabashedly let his eyes wander over the sultry, blue flush of his bones. For a moment it looked like he was about to kiss Sans’ pubis, and Sans braced for it, but what he didn’t expect was for Mettaton to grab his hoodie strings in one hand and curl his fingers through his ribs and around his sternum with the other, pushing him to the bed. The hoodie strings were effectively a leash, pulling Sans’ head up so he could only look into Mettaton’s eye.

“Say it like you mean it,” Mettaton growled, eye flashing dangerously, his canines glinting from Sans’ glowing magic and his own bright soul. “Tell me how much you love this, beg for it, or you won’t get any.”

Sans sucked in a breath, or sounded like he did. He felt his magic churn downwards from the threat and the command. “i--” He whimpered as Mettaton pulled his hoodie strings and twisted his hand where it pushed his shirt between his ribs. “i… i love this!” His voice cracked, “i love how you, mmm, how you touch me, how you know all my spots, how you make me yours, how you talk to me-- agh!”

“Don’t you  _ dare _ stop, gorgeous,” Mettaton growled from the side of Sans’ neck, “Keep going, or this is all you get.”

Sans felt the heat concentrate in his face as he tilted his head back and covered his face with his arm. It was hard to concentrate when Mettaton was biting him how he was. “fuck me! touch me, suck me off,  _ use _ me, make me cum! i want you so bad!”

Sans screeched when Mettaton bit down much harder than he had before, for a moment uncertain of if his HP would be intact for the main event. Mettaton surfaced from Sans’ neck, placing his hands on his shoulders and curling over him so his head was bowed just over Sans’, his teeth glistening and eyes flashing with absolute need. “Call my name, darling!”

“mettaton!” His cry ended in a gasp as his hoodie was all but torn off him along with his shirt, and while his hands were above his head, Mettaton took the liberty of tying his hands with his hoodie sleeves while they were up there.

“mettaton!” It came out as more of a sob as Mettaton’s hot tongue ravished his ribcage, leaving no rib dry. Mettaton sucked on the ends of his floating ribs and Sans felt his pussy form, and Mettaton noticed too. Almost immediately, two of Mettaton’s fingers were knuckle-deep inside Sans, already curling right on his g-spot. Mettaton was leaning on Sans’ bound hands while he fingerfucked him, and he opened his soul chamber so his arousal could drip all over Sans’ spine and pelvis.

“Make a body for me,” Mettaton was now using three fingers and it was all Sans could do to wrap his legs around Mettaton so his squirming didn’t hurt him, but he complied with a hazy mind regardless. His ecto-body went from his knees to his shoulders and was flat-chested and had just a bit of chub, which Mettaton always took great pleasure in. “Summon your breasts too, darling, and I’ll give you something special.” Mettaton had lowered his face right next to Sans’ head, his voice all electric whisper and excited static. Sans did so, his breasts slumping to gravity once they were formed, the left one immediately suckled upon by Mettaton. Almost immediately, his back arched as all three fingers inside him started violently vibrating, as did the thumb rubbing his clit in circles. He gasped and arched his back, rolling his hips into the new stimulation. His eyesockets widened and lit up as he felt himself suddenly thrown to the edge of orgasm.

“metta, i’m gonna--”

“Going to what, Sans?” The vibrations suddenly ceased before Sans could finish, and he slumped, a panting, needy mess. Goddamn him, he didn’t even stop sucking his nipple while he spoke through his speakers.

Sans whined, “mettaton, please! i’m so close! let me-- ngh!” Mettaton removed his fingers and spread them, admiring how they glowed before licking them off, one by one, sucking them as deep as he had thrust them into Sans. Sans made a sound quite like a quiet wail as he wrapped his legs tighter around Mettaton, trying to get him to keep going, but Mettaton refused. He did hear the plates on Mettaton’s groin open and form something, but he couldn’t see that something due to his angle. There were other things on his mind, as he was too far past coherency at that point.

Sans didn’t really question it as he watched Mettaton reach into a compartment in the back of his thigh and pull out a relatively short double-ended dildo, his mouth watered at the sight of it in fact. Mettaton stored in his thighs a few different toys he could choose from when picking out which cock he wanted to pound his partner with. The double-ended dildo definitely wasn’t something Sans would be enjoying by himself, however.

Mettaton set the dildo on the bed and lifted Sans, moving him himself instead of asking him to move toward the head of the bed where he propped the skeleton on the pillows, elevating him a bit. A slick finger slid up against Sans’ clit, making him roll his eyelights back. It truly was adorable how sensitive Sans’ cute little pussy was, Mettaton chuckled to himself. He turned to grab the dildo and faced Sans, drinking him in. His face was bright blue, his teeth clenched shut and his eyes half lidded as he waited for Mettaton’s incoming assault on his waiting body. Sans looked so good when he just couldn’t wait to be touched. His pussy was dripping a bit, his hands still tied, but covering his lovely pair of breasts. Mettaton pursed his lips. That wouldn’t do, but he would deal with that in a moment.

Mettaton picked up the dildo and considered it next to Sans’ tiny body. What couldn’t fit inside him, Mettaton would definitely be able to fit into himself. He started pushing it into Sans, and it resisted for a moment before it popped in with a bit of coercion. Sans jerked and gasped as it was shoved in the rest of the way, calling out something that might have been an attempt at Mettaton’s name. Mettaton smiled at that, leaning up to give Sans a kiss. Sans couldn’t get any stimulation without Mettaton using the dildo, too, but he tried, bucking his hips even as he felt his mouth being ravaged.

Sans felt Mettaton remove himself and kneel between his legs. He positioned Sans’ arms so they stretched downwards, his breasts squished between his elbows, his jacket spread across his hips and stomach. Finally, much to Sans’ relief, Mettaton began edging the dildo inside himself as well. His own pussy had started dripping almost as gratuitously as Sans’ despite the differing amounts of control the two had over the situation. Mettaton positioned his right leg to drape over Sans’ left and his own left leg to fit snugly under Sans’ right. 

With this position, Mettaton quite suddenly shoved his hips into Sans’, pushing the dildo fully into himself and cramming it a little farther into Sans. Sans squealed at that while Mettaton grasped at his hair and allowed himself a long, honest moan, his head thrown back and eyes closed. The dildo was pushed all the way to his soul chamber, and it was exquisite how the head peeked inside just a bit. His chamber’s membrane was very sensitive, after all, and he was being rubbed just right. Mettaton bit his lip, his clit was so close to Sans’. Once they recovered from Mettaton mounting the toy, Mettaton told Sans, “Go ahead, darling. I know you want to cum.”

He grinned, grabbing Sans’ hands so he was sat up a bit and he had a full view of his swollen breasts. Almost immediately, Sans braced himself on his feet and started wildly thrusting his hips.

Whatever submissive atmosphere Mettaton had ensnared Sans in was quickly fading away now that he had at least partial control. His sockets lost the hazy, sheepish glow, and one darkened while the other lit up in a bright blue glare. His position was a bit humiliating since his breasts were bouncing along with his thrusts, held together by his arms and his hands held in place as they were, but it just made him more eager to break the robot under him out of that smug expression. 

He had to stop his head from rolling back as he glared at Mettaton defiantly, the dildo was stretching him so nicely, and he could hear the noises their pussies made as they connected with every jerk of his hips. When he looked down, he could focus more on getting their clits to touch than the pleasure that was coursing through his bones, and it wasn’t long before Mettaton’s dramatic moans began glitching and cutting out. The pleasure was overloading his system and it was trying to shut down his voice to process the sensations, but the louder he screamed the harder it was for that to happen.

Sans groaned as the dildo became quite sticky in its movements, both from his own and Mettaton’s cum and the fact that they were both clenching so hard around it. Any semblance of dominance between either of them had left as their heads rolled back, panting and moaning as they both rolled their hips against the other’s wildly. So close…

Mettaton cried out, not in completion but in frustration. Despite the animalistic pace they had set, it apparently just wasn’t enough for him. He hooked his heels over Sans’ shoulders, releasing his hands and snatching at his femurs. Sans could only reach up to scrabble at the pillows, his jacket being pulled up to partially obscure his face, as Mettaton manipulated his light body into meeting his hips in a brutal pace that surely would have bruised them both if they were capable of it. Mettaton’s thumbs, intentionally or not, were rubbing grooves into his femurs and sending sparks up his spine from the ferocity of both the pace and Mettaton’s possessiveness.

Mettaton wasn’t even paying attention to what he sounded like at that point, completely focused on wrecking Sans and the noises he was making. He couldn’t see Sans’ face very well behind his jacket, but what he could see was the entirety of his face glowing blue, his white eyelights dilated and bright in aroused magic, his sharp canines slightly parted in a cry, that cute, blue tongue that knew his body so well. Sans’ spine suddenly arched violently, a cry ripped from his throat, those canines parted while he screamed. His soul was glowing brilliantly in his ribcage, illuminating the room in bars of light. His legs and arms had stiffened upon his orgasm and Mettaton could fully see his face with his jacket out of the way, tilted back and contorted in an overdose of ecstasy as it was. Sans was clenching so hard that the dildo was practically stopped inside him, meaning it was moving much more vigorously in Mettaton’s pussy.

Mettaton gripped Sans’ femurs tightly as he, too, cried out a broken, “Oh yes!”, Sans groaning at the pressure on his sensitive bones. His soul shone a spotlight on the ceiling, moving towards the door as he arched his hips. He jerked his hips a few times, his voice giving in entirely a few times as he milked his soul for all it was worth, for much longer than Sans could stand without attempting to stop him for the overstimulation it was giving him. Eventually all movements ceased between the two, the only sounds being their heavy breaths and quiet groans as their shifting caused the dildo to move inside them. The dildo was spattered in hot pink and dark blue release around the middle, and would surely be around the ends when it was pulled from the snugness of its users.

Sans was the first to withdraw, whimpering softly as the object squelched out of him, feeling drained and quite like he needed to hold someone while he slept. He peered into Mettaton’s face; Mettaton didn’t appear to have restarted since his chinks were still glowing and he was shuddering in his remaining aftershocks, possibly still clenching around the toy himself just to make it last longer. Eventually his eyes flickered open, half lidded, and he looked at Sans with fluttering lashes. “Darling, won’t you please take this out of me so I can wash it?”

Sans hummed his assent, tracing the toy near Mettaton’s pussy before firmly gripping it and slowly pulling it out, Mettaton groaning in overstimulation as he did. Mettaton rubbed his face and sat on his knees so as to not dirty the bed, making to move off the bed before Sans suddenly straddled him with speed Mettaton hadn’t yet seen. “Sans, what--”

“you were going to clean this, right?” Sans held the long toy up to Mettaton’s lips, quietly loving the cornered look in his widened eyes. “get to it.”

Mettaton glanced between the length in Sans’ hand and his sultry eyes once, twice, before letting his own slip closed, his lips giving way for the toy to enter his throat. The toy wasn’t too big by double-ended standards, but he was barely halfway down it when Sans started shoving more in without Mettaton bobbing forward himself. Sans’ phalanges were tangled in his hair, some getting caught in the chinks of Sans’ knuckles, so he couldn’t escape as the toy continued down his throat. Mettaton couldn’t choke, but he did ask Alphys to give him a fake gag reflex, much like what either of his skeletal boyfriends might feel if something like this was pushed so far into their mouths, simply a pressure on their magic and a feeling like choking while being completely able to function and even speak, provided the object wasn’t getting in the way of their teeth.

The toy wasn’t long enough to extend all the way into his soul chamber from his mouth, but he did begin squirming the closer it got to that point. It was more than three quarters of the way in, his eyes were watering, Sans was cooing something indiscernible to him, probably something about him doing well, but there was fuzz in his hearing apparatus and dear god, it was  _ still _ going in-- And suddenly it wasn’t. Sans had leaned back onto Mettaton’s knees, phalange-tip digging into the head of the dildo that was chest-deep inside Mettaton, just to gaze into his face and watch him squirm with his mouth all plugged up. Mettaton had to stare down his nose just to look at Sans, who was sporting a genuine Cheshire smile. A puff of exhaust left the plates just under his arms in imitation of a flustered huff, and he snapped through his speakers, “I can hardly see how me being in such a compromising position is helping to clean off this toy at all.”

Sans’ grin only split wider. “i can assure you, you’re helping.” He allowed himself a chuckle as he watched Mettaton grab him by the wrist and pull out the dildo so his mouth and speakers could align while he talked again. It wasn’t that it felt unnatural to forgo the physical, mouth-related cues of speech, he just didn’t enjoy talking with his mouth full. The toy was pulled completely out of his mouth, and both watched as his pink-tinted saliva dripped gratuitously off of it and onto their (mainly Mettaton’s) laps for a moment, both flushing at the sight before Mettaton grabbed the toy and put it back into his compartment. His body would clean it automatically once it was put in its place, a genius addition to his body if not for the fact he needed a major update every time he wanted a new toy to account for the programming and waterworks involved.

Sans was looking at Mettaton with hooded eye sockets, and not because he wanted to do more. Mettaton sighed softly and scooped him into his arms again, returning to the couch so Sans could continue his nap while they waited for Papyrus to come home.

~~~

Papyrus set down one of his grocery bags by the door, opening it with his newly freed hand and kicking it in with his usual amount of boisterousness. It clacked quietly with the door spring they had installed on the wall under the dent the doorknob had made after years of energetic door-clanging.

Papyrus picked up his bag again and was about to announce his presence to the other monsters in his home before he caught sight of them curled around each other on the couch, sleeping soundly as the muted television vied for their attentions. They looked so cute like that! Like they hadn’t just accidentally fucked without knowing he was in the house. Papyrus sighed a chuckle and closed the door behind him, quietly (for the Great Papyrus’ standards, nyeheh!) making for the kitchen to put away his groceries. He would unpack his groceries and start dinner, saving his affection for after his boyfriends woke up no doubt due to smelling the saucy masterpiece he was cooking up that night: Spaghetti, of course!


	4. Chapter 4

Papyrus had had just about enough of not being invited into Mettaton’s and Sans’ kinky escapades. By all means he shouldn’t know they were happening, but he could be just as sneaky and quiet as Sans if he wanted to be. He knew what they did and he knew why they weren’t telling him, and it boiled his bones. Monsters always got this strange misconception that he’s some untaintable being locked in his own ways, whatever that meant! He had thought that would end when he gave his body up to Sans and Mettaton, but it seemed there was always more and more levels of impurity he was barred access from by his supposed peers.

These frustrations are why Papyrus specifically chose dinnertime alone with Sans to bring it up. He’d give his darling brother one more chance before he dropped his bombs hard and heavy.

“SANS? DO YOU KNOW WHAT THE LETTERS ‘BDSM’ MEAN?” As expected, Sans choked on his noodles while Papyrus waited in wide-eyed patience. “ghk-- what? do you?”

Papyrus faked a smile, as bright and wide as always. “OF COURSE! BUCATINI, DITALINI, SPAGHETTI, MATRICIANI!” His brother’s sockets were wide and his mouth was forming his next answer, but before he could even try, Papyrus dropped his smile and gave Sans a rather bleak look. “Listen. I know what you two have been doing without me.” His eyesockets narrowed. “I’m more perceptive than you give me credit for, brother, and I think I’m just about done playing the naive sweetheart with you two.”

Sans’ face, a flustered blue before, had blanched as he realised how right Papyrus was. He knew he was still looking down on Papyrus as his little brother, but he thought he’d been doing much better since they started dating. It wasn’t that he thought Papyrus was too immature for rougher, more kinky activities! If anything, with all the rules and precaution and forethought that went into things like that, Papyrus would be an ideal partner in that kind of situation. Sans just also knew that Papyrus’ standards would probably lead him away from anything too cruel or unfair, and that’s the kind of stuff BDSM was made out of. “bro, that’s not it at all… heh, i mean, you do have a sweet heart, but that’s not why we didn’t include you.”

Papyrus’ gaze made him feel like he was sitting with a blue attack phasing through his neck, like if he made the wrong move… He swallowed, Papyrus’ desire was practically dripping off him and down the legs of the table, and Sans wanted to step in it and get twisted up and devoured by it. “we th… we thought you’d hate it. you’re a fair guy, bro, we didn’t want to offend you by playing dirty.” Papyrus’ expression relaxed a fraction, but he kept his penetrating stare.

“Who says I can’t play dirty, too? I think… Sometimes you have to be a little unfair if it means you’re helping someone out in the end. If you’re giving them what they want, it’s not cruel, is it, Brother?” The areas around his eyesockets were glowing orange.

Sans was a little horrified to feel his magic on the brink of forming in his shorts, feeling trapped like a moth in a jar, trying not to flutter around or risk damaging his wings and his ability to escape quickly. His soul pounded under his ribs. “n... no, it’s not, i guess.” He could feel Papyrus’ foot rubbing up toward his femur under the table, wrapping under and lifting his leg to the side, settling on the front of his pelvis. Papyrus suddenly stood and crossed behind him, setting a gentle, gloved hand on the side of his neck. Sans brought up his own hand to it to cling to the heat it brought to him but it didn’t hit him until too late that Papyrus was  _ standing on the foot that was supposed to be shoved into his groin _ \--

As soon as the shock and confusion registered on his face, the limb coiling on his leg tightened, and a similar sensation manifested around his opposite arm. The smell of Papyrus’ magic pushed his magic to form in turn, and his shorts immediately stuck to it. Before he knew it, he was being lifted by those limbs- When had Papyrus practiced making tentacles? Without him knowing, too?- and Papyrus was removing him bodily from the dinner table, carrying him with his magic like it was nothing while coiling them around and around his limbs and rubbing against his pussy and reaching up toward his ribs. “And what do you think is more unfair? Satisfying your partners or being so  _ starsdamned _ charming and cute they take it out on each other instead of you?”

He dumped Sans on the couch, spreading his knees apart with his legs and letting his tentacle weave through his radii and ulnae and pin his arms above his head. “Well, Sans?”

His eyelights blown wide, he held his breath and replied, “it is unfair, paps. you’re just too good. you... you could even it out. me ‘n metta would let you. it would, heh, it would be cruel of us not to let you in if you wanted to play dirty. so please...” He arched his pelvis up toward Papyrus, where one of his tentacles was working his shorts down and rubbing its rounded side against his pussy as it did. “dirty me as much as you want.”

Papyrus grinned harshly and filled Sans’ pussy with his tentacle, reveling in the cry, the evaporated eyelights, how tight and wet his big brother was for him.

~~~

Later, resting on Papyrus’ bed with Sans laying on his ribcage, Papyrus pet Sans’ skull. “WAS IT TOO MUCH, BROTHER?” Sans groaned, but tilted his head up. “no, you’re a natural, bro. mettaton’s gonna love this.” Papyrus glowed and slipped his sockets shut.

“I WANTED TO ASK YOU SOMETHING ABOUT HIM, ACTUALLY.”

“hm?”

“I WANT TO MAKE HIM FEEL HOW I MADE YOU FEEL JUST NOW. I WANT TO DO SOMETHING TO HIM HE’LL REMEMBER, AND I CAN’T STOP THINKING ABOUT IT. I’D LIKE YOUR HELP, I KNOW YOU’RE MORE ACQUAINTED WITH HIS… INNER TECHNOLOGY.”

“what did you have in mind?”

He wriggled his shoulders and took a deep breath. “I want to fill him up right before he goes on camera. I want to watch the fear in his eyes while he struggles to hide our cum splattering the inside of his soul container.”

Sans cursed quietly at his tone. “fuck, paps.”

“DOESN’T IT SOUND FUN, SANS?”

“stars, of course it does, bro.”

“SO YOU’LL HELP ME?”

“what would that entail exactly?”

“TELL HIM WHAT WE WANT TO DO TO HIM, BUT LEAVE ME OUT UNTIL IT’S TIME TO FILL HIM UP. THEN, I’LL MAKE MY GRRRAND-” Sans snorted. “-ENTRANCE AND TAKE CHARGE OF OUR ROBOT-STUFFING DUTIES. AFTERWARDS, WE’LL JAM HIS COOCH MECHANISM AND WELD THE METAL BITS SHUT. THEN MAYBE LATER WE’LL STRING HIM UPSIDE DOWN SO WHEN WE FIX HIM BACK UP NONE OF IT DRIPS OUT…” There was a wet spot of blue drool on Papyrus’ nightshirt.

“yeah, that… sounds great. more than great. how long have you been thinking about this, bro?”

Papyrus winked and softly clanked his teeth to Sans’ forehead. “HOW LONG HAVE YOU TWO BEEN DOING THINGS LIKE THIS BEHIND MY BACK AGAIN?”


	5. Chapter 5

“Darling!” Mettaton bowled into Sans, wrapping his arms around him a few times while he buried his screen into his little skeleton’s chest. Before they hit the ground, Sans flicked his blue magic at the doorknob to close it.

“hff, good to see you too, metta, heh. have you lost weight?”

Mettaton chuckled quietly. “Is Papy home, gorgeous? Or do we get to play one-on-one today~?” He began unwinding his arms and pushing himself back up on his snow-tread. Alphys made it for him just in case he ever needed to go to Snowdin in his BETA form, and that was quite often now that he had lovers living there.

“we get to play real rough today, metta. i’ve got a fun idea i bet a freak like you would enjoy… c’mere.” He flashed a devious grin while he teleported them both onto his mattress, Mettaton still in the process of retracting his tread in favor of his wheel.

“Ohhh!” he hit the bed on one of his edges, flopping down on his front, then his switch was flipped, and before he could even say anything his boxy body was retracting and his legs and human-imitation body were flipping into place and stretching out in a puff of pink smoke. Panels rotated and shifted all in the span of five seconds and left Mettaton lying prone in his EX form. “Woah, quick on the draw today, are we darling?”

“heh. maybe. how about i tell ya when I have in store for you today?” Sans sat on Mettaton, a knee on the small on his back and his shin on the bed. He placed a hand on the back of Mettaton’s neck when he turned to Check him to gauge his intent better. “you’ve got a music video to record tonight, don’t you? lots of fancy skirts and tuxes tonight, right?”

“Hhh… Yes? Why?” He could feel his genitals warming in his pelvis area, burning to burst free and be touched as he sensed the danger in the room. It  _ thrilled _ him. Had he need for breath he’d be panting in anticipation.

“well, i figured since i’m the only mechanic you’ll fuck, we could play around with my skills on your body. specifically...” He turned Mettaton’s body around so he could look him in the eyes, forcing him to support himself on his elbows. “we wanna stuff you with cum, weld you shut, and watch you struggle to hold it together in your music video. if you’re careful, the cameras won’t pick up the mess we’ll leave inside you, okay babydoll?”

Mettaton tensed and his eyes flashed a shocked yellow. “W-We… Who… You’re gonna… Wait, Sans?!”

Sans turned the switch on Mettaton’s hip to present his vagina while Papyrus stepped out from behind the door, shutting and locking it. “Fuck!” His artificial nerves activated in his pussy and he throbbed while Papyrus strode further into sight. Sans cackled when the Metal Gear exclamation mark sound effect rang out of Mettaton’s speakers, and he found himself so flustered and caught off guard that the vents in his neck started humming as his internal fans expelled the heat on his face. “Papyrus, when did-” Papyrus kissed him and snaked his long tongue down his throat. He was half-kneeled on the bed, one hand in his boyfriend’s hair and one curled into a fist while his elbow supported him. In that position, Mettaton’s chestplate and Papyrus’ battle body rubbed together, pelvis and pussy inches apart.

Papyrus released Mettaton, who had heart-shaped, shocked-yellow eyelights. Papyrus liked to think it was one of the first times his eyes ever had that combination. “GET OFF HIM AND HOLD HIS HANDS DOWN, WON’T YOU, DEAR BROTHER? I WANT HIM TO LOOK AT ME.”

Sans did so and Papyrus straddled his soul chamber, reached out to grasp his face in one large, gloved hand so he could peer into his robot’s eyes with smoking eyelights.

“Papy, when did all this happen…?” He arched his chest up and batted his eyelashes, hoping his boyfriends would have mercy on him. Papyrus ignored him. “YOU TWO AREN’T VERY CAREFUL. OF COURSE I’D KNOWN ABOUT BDSM BEFORE I SAW YOU, BUT SEEING IT IN ACTION BETWEEN THE LOVES OF MY LIFE… I WAS SICK THAT YOU HADN’T EVEN INVITED ME, SO I INVITED MYSELF. YOU’RE FINE WITH WHAT I HAVE IN MIND FOR YOU?” He let go of Mettaton’s face and stroked down his cheek with the backs of his fingers.

“Ah...” Papyrus scratched down to his neck and behind his ear. “Did we hurt your feelings, Papy? Leaving you all alone?” He pouted, sticking his lower lip out. “Did watching us play without you upset you? Make you wanna fuck me?” He smirked, seeing Papyrus’ crinkled brow bones. “Or did you resent being treated like a babybones? Like you couldn’t handle playing with the big boys? So now the Great Papyrus feels like he has something to prove-”

Papyrus slapped a hand over his mouth. “SANS! WHAT IS HIS SAFEWORD? WE’RE GOING TO FUCK HIM SENSELESS! SHUT HIM UP WITH YOUR COCK FOR ME, WON’T YOU?”

“stars yes, it’s ‘stop rolling’.”

“He won’t shut me up like that, darling!” Mettaton teased through his speaker, almost overpowering Sans’ soft, bewildered murmur. “NO, BUT IT’LL SHOW US WHO CAN’T HANDLE PLAYING WITH THE ‘BIG BOYS’, WON’T IT? WE HAVE A FEW HOURS TO COMPLETELY DESTROY YOU, AND WE’LL GET TO WATCH YOU TRY AND FAIL TO PLAY IT OFF ON THE UNDERNET OVER AND OVER AND OVER, AS MANY TIMES AS WE WANT.” Papyrus removed his hand just long enough for Sans to plug Mettaton’s mouth with his fat, blue cock, moaning giddily while Mettaton sputtered.

Papyrus slipped his dick out of his shorts and lined up to shove in, to a crackle of Mettaton’s speaker: “Wo-woah! Already? You’re usually so careful to prep-”

“NOT TODAY, SWEETHEART! I CAN TELL YOU SPENT A LOT OF TIME PREPPING YOURSELF ALREADY.” He thrust in and Mettaton screeched through his speakers, glitching them in shock. Sans had turned around and had his knees on the sides of his head, curled over his boyfriend while he used his throat to jerk off. He held his head in place, leaving no wiggle room between his hands and his pelvis.

Meanwhile Papyrus did still for a moment to savor the feeling of Mettaton’s constantly tight pussy and to give him a moment to metaphorically breathe before pounding him. He masked the small kindness by placing his hand on Mettaton’s soul chamber and rubbing his thumb over the glass, looking at the head of his dick peeking in. He puffed, drew out to the very tip, and slammed back in, using his momentum to set a brutal pace that had Mettaton squeaking and moaning appreciatively. The room echoed with a percussive symphony of bone on metal and synthetic flesh. Papyrus hadn’t anticipated the view of Sans’ sacrum gyrating in small, quick circles over Mettaton’s face as being quite so alluring with the soft pants coming from him. Papyrus had to bite his tongue to keep a non-dominant noise in just from listening to the noises the pair under him was making. Mettaton’s soul was drooling and making his pussy even more slick, dripping pink on the already dirty sheets and making sticky noises with each snap of Papyrus’ hips. He was absolutely living for it, drinking in his robot’s noises, eyelights positively glowing while he felt himself get close already-

“D-D-D-Ah-Ah-Ah-arling I’m-m-m-! N-N-Ngh-Ah-Ah-Ah-” His poor voicebox. Sans would need to give him a quick tune-up later on for his music video so he wouldn’t sound absolutely ragged in the recording.

“A-AAAAAGH!” Mettaton’s back arched, tipping his soul chamber back and just about throwing Sans off him. It was all Papyrus needed to let himself go, clutching around his robot’s gorgeous hips and clinging to him, smashing their pelvises to each other and releasing thick ropes of bright orange right into his soul container, pussy be damned. Some of his cum shot straight onto his soul, which Papyrus imagined would give him an intense burst of Papyrus’ intent, but some splattered on the glass and dripped down thickly.

“A-Ahhh fuck- ghk!” Sans came down his throat and Mettaton swallowed reflexively. The magic didn’t dissolve in his mouth like monster food but dribbled down the top of his soul chamber. That hadn’t been part of Papyrus’ plan but he was thrilled to see that it worked. He allowed only a moment to go by before he pulled Sans into his chest with a wet  _ pop _ when Sans’ cock was extracted from Mettaton’s throat. He fisted Sans’ cock in his hand while he looked at Mettaton’s face, covered in his own pink spit, a little blue cum, and an expression of curious, intense desire. He still looked a bit bewildered at the situation. Papyrus clanked Sans on the cheekbone and pulled out of Mettaton. “Switch,” he murmured against his flushed skull, and Mettaton must have caught it because he looked a little scared to take Papyrus’ monster cock down his throat.

“AWW, DON’T WORRY, SWEETHEART.” Papyrus sat on Mettaton’s chest and rubbed his dick on his cheek. “YOU CAN HANDLE US FOR ANOTHER FEW HOURS, RIGHT?”

Mettaton moaned quietly, deep in his chest, grabbed Papyrus’ hips and turned his head slightly to kiss the side of his dick. “Bring it on, sugarskull.”

Papyrus grinned widely.

~~~

Sans, always a monster of endurance without stamina, had taken to pumping his hips fast and shallow. He’d cum twice this round before his partners had cum once and was well on his way to a third. That was his role here, to cum as many times as he could inside this stupidly sexy robot. “ugh-” He clung to Mettaton’s curvaceous hips for the third time that round and came hard, watching between Papyrus’ legs Mettaton’s throat as the fleshy bit was rhythmically stretched in time to Mettaton’s slightly pained whimpers. If Sans moved off to the side, he could see Mettaton’s eyelights were hot pink hearts staring right up into Papyrus’ face. His brother was so cool.

~~~

Mettaton’s head was spinning between the cocks in his mouth and in his pussy, and his fucking incredible skeletal lovers. He could hardly tell where one orgasm ended and where one started, there was so much to pay attention to like the sloshing of blue and orange cum, the physical and emotional sensations it wrought on his soul. It felt like a drug, feeling their intents literally washing over his core. Stars, he was cumming again--

~~~

At some point Papyrus lifted Mettaton by the thighs with his ridiculous physical-law-breaking power, bending him in half and pinning his arms so he could get at his ass while Sans continued slamming his poor, wrecked pussy. He panted into Mettaton’s chestplate, keeping his auditory meatus far away from Mettaton’s crackling speaker. Papyrus was biting into his neck and shoulder while fucking into his ass, taking care not to break through the flesh but making speech all but impossible and holding their robot upright by a hand on his throat. Papyrus’ hand clamped down on Mettaton’s throat while the pool in Mettaton’s soul chamber bubbled and stirred with fresh cum, and Sans came while Mettaton’s cunt clamped around him in kind. His soul container was filled halfway to the tip of his soul with all their combined cum. When Sans looked up, Mettaton’s face was upturned, eyelights invisible from his angle but dulled pink from exhaustion. The only way to tell he was still conscious was the soft “Ah, ah, ah...” coming from his speaker.

~~~

They had pushed their robot face-down into the mattress, Sans brutalising his ass while Papyrus hugged them both and slammed Mettaton’s now abused cunt. He couldn’t remember the last time his pussy was so raw. They had turned him onto his front with his ass in the air because their cum had started leaking out from its own weight. Mettaton came around them again, making them both groan in overstimulation, then hiccuped. He tasted something fruity in his mouth and dragged a finger across his tongue to find a glowing, off-white substance. He would have to keep swallowing it all down every time he hiccuped. He didn’t even know he had that feature, it was the first time he hiccuped in his robot body.

~~~

Sans finally tired out and took the opportunity to make out with Mettaton while his brother railed him from behind, running his comparatively small hands over as much of their robot as he could. Overstimulated tears streamed from his ducts but he still didn’t call his safe despite them both keeping an eye on his speaker to make sure he could even still talk. Sans pressed his small body into Mettaton’s chest and bit down into his neck and Mettaton came again with a strained wail.

~~~

Finally even Papyrus tired out and his magic popped out of existence after cumming hard, but without much magic output. Sans had gone downstairs and gotten some water and food somewhere along the line to help replenish the energy they’d need for the second half of their play. Mettaton’s soul chamber was almost totally full of cum and his soul was completely submerged in it, flooding him with synthetic energy for more. If he wasn’t careful, cum could slosh into his throat even while standing up. He found himself nervously anticipating going in front of the cameras in such a state, and intensely grateful to Sans for making sure he was going to be wearing torso-covering clothes. He wasn’t sure the glow wasn’t going to be visible unless he took the time to wrap his chamber in something dark. He felt so empty without a cock stretching him out. So he laid, a spreader bar strapped to his knees and his pelvis raised on a pillow while he furiously masturbated, filling himself with three vibrating fingers, almost squishing his engorged clit with his other hand, which he had vibrating on the highest setting. Barely aware of his audience, he made himself cum over and over again, fuelled by the splashing cum in his chamber and the feelings it was pouring over his soul. He curled his fingers into the artificial nerves deep inside himself repeatedly, until finally there was no more fight left in him and he slumped against Papyrus’ thigh with a defeated whimper. His fingers were still jammed inside him.

Papyrus stroked his hair and cooed at him while Sans got to work between Mettaton’s legs. He worked Mettaton’s fingers out of him and took off his mitten to expose his own phalanges. His hand glowed with green healing magic, which he proceeded to lay on Mettaton’s sensitive vulva. Mettaton moaned and tried to reach down to make Sans touch him more, but Papyrus grabbed his hands and held them above his head. Sans ever-so-gently slid a single finger in, still glowing with green magic, to take the edge off the ache the past few hours drilled into him. Mettaton sighed with relief. He had been stinging a bit. He opened his eyes a little more when Sans brought out something with his pink-and-black brand colors on it, a set of jiggle balls closely connected, thick, and heavy. “H… Hey…” He was too lethargic to move his mouth with his voice.

Sans just winked at him and started inserting the jiggle balls one by one. Stars, his brand was so good, just wiggling his hips was already making the balls shift. Once they were all in, Sans summoned two very thin, small, gray attacks and slotted them in the chinks between Mettaton’s vulva and the part of his groin that didn’t transform when his genitals switched out. He then turned the switch on Mettaton’s hip to retract his vulva, which his gray attacks only allowed to a short extent. Mettaton’s system still thought the vulva was retracted and thus cut off the nerves from sending sensation to Mettaton’s “brain”.

“What are you doing, Sans?”

Papyrus nuzzled into the side of Mettaton’s head and kissed him on the cheek. “don’t worry, i’ll turn it back on here in a minute. i’m gonna weld you shut now, okay doll?”

“Ughhh… Yeah.”

“and afterwards we’ll get you fed and charged, then i’ll take you to your shoot.”

“Fuck the shoot, I just wanna keep doing this… Every day…” He was drifting off now that he couldn’t actually feel anything on his genitals. He remained in sleep mode while Sans welded a piece of scrap metal between the plates in his legs. How hadn’t he seen the equipment when they teleported in? Well, he hadn’t seen Papyrus either. By the time Sans was done, his crotch looked just like it did when he didn’t have any sexy parts equipped. Mettaton only roused when Sans turned the feeling in his pussy back on.

“Agh… Full…”

“heh, you sure are.”

Sans plugged Mettaton into the wall by the charging cord that extended from inside his foot and checked the time on his phone. They still had an hour and a half before Mettaton would need to be in Hotland. That would be enough time to get Mettaton recharged and re-energised before he had to go out in public.

Sans suddenly found himself on his side, pressing into the mattress with a skull aggressively nuzzling his. “I’M SO HAPPY WE COULD PLAY TOGETHER LIKE THIS!” With those sockets, he could have been talking about anything from a cooking date to meeting up for lunch, so Sans snorted at how innocent he looked talking about doing something so lewd. Sans hid his wide grin in Papyrus’ chest.

“aw, bro. so am i.” They spooned for a bit until Papyrus dragged Sans out of bed to shower them both.

Papyrus decided that cleaning his lovers after rough sessions was something he wanted to do as often as possible.

~~~

Sans took Mettaton to his shoot via shortcut when he was done charging, and napped on Papyrus’ chest when he got home. Mettaton called a few hours later for Sans to get him, all hushed, “No darling it went fine,” and “Please just come get me.”

Mettaton was all over them when he got back, begging to have the metal strip removed, to be fucked, to just get the cum drained, anything.

“Please, please darlings, I did it, I feel so full, let me out-” Papyrus was grabbing him and kissing him and Sans was teleporting them back to his room, flipping the switch on his hip, almost having to use blue magic to hold him still. He worked through the motions quickly, dissipating his gray magic, letting everything slot into place as it was designed, except that cum was immediately rushing out and he had to plug the robot up with his whole hand.

“shit! paps, grab that- yeah, thank you.” Papyrus handed him the bucket he put behind his mattress with the welding materials just in case this happened. Sans and Papyrus soothed Mettaton while he purged his load- their loads- moaning and writhing all the way. If they didn’t know him any better, the thought of him faking some of it to get them to touch him more wouldn’t have crossed their minds. Eventually Mettaton was emptied and the bucket filled almost to the brim. Papyrus left the two of low energy to rest while he got a rag to clean Mettaton up, and Sans’ hands where he got hit with the splash. He carried the two clean monsters to his greater, cleaner room and set them on his racecar bed, then set out to do something about the bucket of swirling vulgarity left in Sans’ room. When he returned, the two were curled up together, Sans with his tiny form pressing up on Mettaton’s chestplate and chamber and one of Mettaton’s noodly arms hugging him about the chest.

“Nyeh.” He supposed he would answer any of Mettaton’s questions about their new bedroom arrangements in the morning.


	6. Chapter 6

**Notes for the Chapter:**

> Small epilogue.

A whole month later, the music video debuted on the Undernet. The two skeletons and their robot clamored around Papyrus’ PC to see how he did at covering his lust. Mettaton had been so flustered the day of recording that he refused to look at the editors’ screens, but he was regretting it now that he was viewing himself alongside his thousands of fans. The video had him wearing a short, black, strapless dress with a flowing skirt that cascaded to his ankles. Without the waist trainer he stuck on his chamber’s glass, it probably would have been visible. Later on he was wearing a white tuxedo with a gaudily decorated top hat, which he threw behind the camera while spinning with his face upturned for an aerial camera shot. The camera zoomed on his face and his expression faltered just slightly as if he’d gotten suddenly nervous, but quickly reverted to his usual charisma and confidence. It was a fraction of a second, unnoticeable to anyone who wasn’t looking for it. His eyes were hot pink hearts in the entire video, but it was hard to tell until that scene. Mettaton’s face heated thinking about his sharp-eyed fans who might have caught the shape of his eyelights and went back to watch the video scene-for-scene to look directly into his face. Thinking about rumors about him that could have been going around, what could have caused the very slight body language change, the conclusions his fans drew… It made him feel a twinge of nervousness before he was overcome with giddiness and excitement. Before the video was over, Mettaton was giggling and hugging his skeletons close to him.

“Haha! Papy, what was that you said about me trying and  _ failing _ to hide what you had done to me?”

“NYEH! I WILL CONCEDE… YOU ARE EVEN GREATER THAN I HAD EXPECTED TO KEEP YOUR COOL THROUGH ALL THAT!” Papyrus nuzzled his skull into Mettaton’s neck affectionately, making him giggle more.

Sans was downloading the music video during this interaction, and he sat himself in Mettaton’s lap. “pretty impressive that you weren’t wigglin’ around with that toy in ya, Metta. We should do things like that more often.”

“NYES!!! IT WAS SO FUN SEEING HOW YOUR BODY MOVED BEFORE YOU PUT ON YOUR ACT. AND HOW YOU JUST KEPT BEGGING US FOR MORE...” He held the hand that was wrapped around him and graced Mettaton’s neck with his fangs.

“I hope you don’t mind if we make this a more common occurrence. I think your fans would enjoy seeing you writhe, hm?”

Mettaton shivered. “I… Think that can be arranged, darlings. Please.”

**Author's Note:**

> Wait for it...


End file.
